[JENKINS-68904] More stylelint fixes

[NotMyFault]

Addresses the stylelint part of JENKINS-68904, ESLint is still up to do.
Stylelint errors are no longer shifted to warnings, new introduced issues will fail the CI build.

Proposed changelog entries

• Entry 1: Issue, Human-readable Text
• ...

Proposed upgrade guidelines

N/A

Submitter checklist

• (If applicable) Jira issue is well described
• Changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developer, depending on the change) and are in the imperative mood. Examples
  • Fill-in the Proposed changelog entries section only if there are breaking changes or other changes which may require extra steps from users during the upgrade
• Appropriate autotests or explanation to why this change has no tests
• New public classes, fields, and methods are annotated with @Restricted or have @since TODO Javadoc, as appropriate.
• New deprecations are annotated with @Deprecated(since = "TODO") or @Deprecated(forRemoval = true, since = "TODO") if applicable.
• For dependency updates: links to external changelogs and, if possible, full diffs

Desired reviewers

@jenkinsci/sig-ux

Maintainer checklist

Before the changes are marked as ready-for-merge:

• There are at least 2 approvals for the pull request and no outstanding requests for change
• Conversations in the pull request are over OR it is explicit that a reviewer does not block the change
• Changelog entries in the PR title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood
• Proper changelog labels are set so that the changelog can be generated automatically
• If the change needs additional upgrade steps from users, upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the PR title. (example)
• If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).

[timja]

Thanks for this, could you push a new issue to show the build failing please? and then revert.

[NotMyFault]

Thanks for this, could you push a new issue to show the build failing please? and then revert.

Without modifying the lifecycle the build doesn't fail if errors are detected, but I'm not too sure if the latest commit is appropriate. According to ci.j it doesn't seem so.

Any recommendations? <phase>test</phase> is too weak to cause a build failure, based on the prior logs 🤔

Edit: Looks like I found something that works.

[basil]

Nice cleanup!

[NotMyFault]

@timja The failure can be seen on https://ci.jenkins.io/job/Core/job/jenkins/job/PR-6792/6/consoleFull, I'm going ahead and revert the commit introducing it.

[timja]

This PR is now ready for merge, after ~24 hours, we will merge it if there's no negative feedback.

Thanks!